When an aluminum plate is bolted to a steel plate, what is required at the bolted joint to minimize bimetallic corrosion?

Correct Answer: Option A — The plates should be electrically insulated from one another by use of non-conductive gaskets and non-conductive ferrule sleeves with the bolts.

Bimetallic corrosion occurs when dissimilar metals are in electrical contact in an electrolyte. To prevent this between aluminum and steel, you must break the electrical path using non-conductive gaskets and insulating sleeves for bolts, effectively isolating the metals to prevent the aluminum from becoming a sacrificial anode.